1. Measurements & Calculations
Chapter 2 section 2

2. Chapter 2 Lesson Starter
Section 2 Units of Measurement
Chapter 2
Lesson Starter
Would you be breaking the speed limit in a 40 mi/h zone if you were traveling at 60 km/h?
one kilometer = 0.62 miles
60 km/h = 37.2 mi/h
You would not be speeding!
km/h and mi/h measure the same quantity using different units

3. Section 2 Units of Measurement
Chapter 2
Objectives
Distinguish between a quantity, a unit, and a measurement standard.
Name and use SI units for length, mass, time, volume, and density.
Distinguish between mass and weight.
Perform density calculations.
Transform a statement of equality into a conversion factor.

4. Chapter 2 Units of Measurement Measurements represent quantities.
Section 2 Units of Measurement
Chapter 2
Units of Measurement
Measurements represent quantities.
A quantity is something that has magnitude, size, or amount.
measurement  quantity
the teaspoon is a unit of measurement
volume is a quantity
The choice of unit depends on the quantity being measured.

5. Learning Check
Label each of the following measurements by the quantity each represents.
5.0 g/mL mg
37 s L
47 J
39.56 g
25.3 cm^3
325 ms
500 m^2
30.23 mL

6. Chapter 2 SI Measurement
Section 2 Units of Measurement
Chapter 2
SI Measurement
Scientists all over the world have agreed on a single measurement system called Le Système International d’Unités, abbreviated SI.
SI has seven base units
most other units are derived from these seven

7. Section 2 Units of Measurement
Chapter 2
SI Base Units

8. Chapter 2 SI Base Units Mass
Section 2 Units of Measurement
Chapter 2
SI Base Units
Mass
Mass is a measure of the quantity of matter.
The SI standard unit for mass is the kilogram.
Weight is a measure of the gravitational pull on matter.
Mass does not depend on gravity.

9. Chapter 2 SI Base Units Length Length is a measure of distance.
Section 2 Units of Measurement
Chapter 2
SI Base Units
Length
Length is a measure of distance.
The SI standard for length is the meter.
The kilometer, km, is used to express longer distances
The centimeter, cm, is used to express shorter distances

10. Chapter 2 Derived SI Units
Section 2 Units of Measurement
Chapter 2
Derived SI Units
Combinations of SI base units form derived units.
pressure is measured in kg/m•s2, or pascals

11. Derived SI Units, continued
Section 2 Units of Measurement
Chapter 2
Derived SI Units, continued
Volume
Volume is the amount of space occupied by an object.
The derived SI unit is cubic meters, m3
The cubic centimeter, cm3, is often used
The liter, L, is a non-SI unit
1 L = 1000 cm3
1 mL = 1 cm3

12. Derived SI Units, continued
Section 2 Units of Measurement
Chapter 2
Derived SI Units, continued
Density
Density is the ratio of mass to volume, or mass divided by volume.
The derived SI unit is kilograms per cubic meter, kg/m3
g/cm3 or g/mL are also used
Density is a characteristic physical property of a substance.

13. Derived SI Units, continued
Section 2 Units of Measurement
Chapter 2
Derived SI Units, continued
Density
Density can be used as one property to help identify a substance

14. Derived SI Units, continued
Section 2 Units of Measurement
Chapter 2
Derived SI Units, continued
Sample Problem A
A sample of aluminum metal has a mass of
8.4 g. The volume of the sample is 3.1 cm3. Calculate the density of aluminum.

15. Chapter 2 Conversion Factors
Section 2 Units of Measurement
Chapter 2
Conversion Factors
A conversion factor is a ratio derived from the equality between two different units that can be used to convert from one unit to the other.
example: How quarters and dollars are related

16. Conversion Factors, continued
Section 2 Units of Measurement
Chapter 2
Conversion Factors, continued
Dimensional analysis is a mathematical technique that allows you to use units to solve problems involving measurements.
quantity sought = quantity given × conversion factor
example: the number of quarters in 12 dollars
number of quarters = 12 dollars × conversion factor

17. Using Conversion Factors
Section 2 Units of Measurement
Chapter 2
Using Conversion Factors

18. Conversion Factors, continued
Section 2 Units of Measurement
Chapter 2
Conversion Factors, continued
Deriving Conversion Factors
You can derive conversion factors if you know the relationship between the unit you have and the unit you want.
example: conversion factors for meters and decimeters

19. Section 2 Units of Measurement
Chapter 2
SI Conversions

20. Conversion Factors, continued
Section 2 Units of Measurement
Chapter 2
Conversion Factors, continued
Sample Problem B
Express a mass of grams in milligrams and in kilograms.